Spanish monarch reportedly expressed a desire to hand the throne to heir while Prince Felipe was still a young man to stop him "withering" like Prince Charles

King Juan Carlos told courtiers that he wanted to abdicate in favour of his son because he did not want his heir to “grow old waiting for the throne like Prince Charles”.

The 76-year-old monarch, who announced last Monday that it was time for “a younger generation to step into the front line,” is said to have been influenced in his decision to abdicate by the situation of the Prince of Wales, who at 65 is the oldest heir to the British throne for 300 years.

It emerged on Sunday that King Juan Carlos had privately told those close to him that he felt it was right to pass the throne on while his heir was still a young man.

“I do not want my son to wither waiting like Prince Charles,” he reportedly told Rafael Spottorno, chief of the royal household, according to a report in Spain’s daily El Mundo newspaper.

King Juan Carlos had been considering the decision since his 75th birthday in January 2013, his chief of staff admitted, and that he had discussed it at length with those in his inner circle.

“He saw, above all, that his son was in his prime and didn’t want to see him like Prince Charles who will be 66 years old in November,” the newspaper quoted Mr Spottorno as saying.

King Juan Carlos is abdicating in favour of his son, Crown Prince Felipe (Gerard Julien/ Getty)

The Zarzuela Palace refused to confirm or deny the statement on Sunday morning. A Clarence House spokesman “declined to comment” on the reports.

“There is a lot being written every day as regards the abdication and we are not prepared to comment on every article,” a spokesman said.

John Prescott, the former Deputy Prime Minister, on Sunday called for the Queen to “gracefully step aside” and allow the Prince of Wales to deliver next year’s address to Parliament.

Lord Prescott said that Her Majesty, now 88, should follow the example of Pope Benedict XVI and the three European monarchs who have abdicated this year and become the “Queen Emeritus” as part of a “gentle succession”.

“Why not let Charles take more of the burden off her shoulders? In 2015, she could hand over the State Opening of Parliament to her son,” Lord Prescott said.

“It could be the King-in-Waiting’s Speech. Though knowing Charles, he’d probably want to rewrite it – especially any bits which were not environmentally-friendly.

“When Pope Benedict XVI stood down last year he became Pope Emeritus. So why can’t we have a Queen Emeritus? Elizabeth has given great service to this country. No one would think less of her if we allowed her to enjoy her remaining years with her grandchildren and great grandchildren as the Queen Mother.”

King Juan Carlos, who was widely credited for his leading role in Spain’s smooth transition to democracy on the death of fascist dictator Gen Francisco Franco, saw his popularity plummet in recent years after a series of royal scandals tainted the crown.

Explaining his decision to abdicate, the king said a generational change would open “a new chapter of hope” for a country hit by a deep economic crisis, and insisted that his son had “the maturity, the readiness and the sense of responsibility needed to take on with full guarantees the leadership of the state”.

The Crown Prince Felipe, 46, who married Letizia Ortiz, a divorced television journalist, ten years ago, has increasingly substituted for his ailing father on diplomatic trips and at official events and is regarded as relatively untouched by the family scandals.

But since the abdication was announced, Spain has seen a wave of protests calling for a referendum on the future of the monarchy. Thousands gathered to hold street demonstrations on Monday evening and again on Saturday to express their republican fervour.

According to a poll published in Spain’s left-leaning El Pais newspaper on Sunday the majority of Spaniards – 62 per cent – believe a referendum should be held “at some point” on whether Spain should continue to have a monarchy.

If a referendum were to be held, the poll found 49 per cent would prefer to have a monarchy with Felipe as king while 36 per cent would support a republic.

Prime Minister Mariano Rajoy has already outright rejected calls for a referendum on the monarchy claiming there is no mechanism within Spain’s constitution that would allow it.

The ceremony to crown King Felipe VI will take place on June 19 following a vote in Spain’s parliament to approve the abdication.

It is expected to be a low-key ceremony held within the Congress building in Madrid to which no foreign heads of state or members of other Royal families have been invited.